Currently, all types of commercial laser CDs, video discs, and computer light discs use disc technology to record digitized signals on different types of discs. These digitized signals are represented by recesses formed in the discs. A protective and transparent coating is applied to the surfaces of these recesses. When the signals are read or picked up, the disc is first irradiated with a laser beam on the surface of the disc and then the signals represented by the reflective beam are read. Though the surface of the disc is protected by a protective and transparent coating, and even though the reading head or the pick-up head do not touch the surface when they read or pick up the signals, nevertheless there is an accumulation of dust, fingerprints, and moisture which have a detrimental effect on the reading and picking-up of the signals from the reflected laser beam. Therefore, it is necessary that the disc surface must be cleaned on a periodic basis.
Because the recesses formed in the disc are aligned in a spiral contour approximating a circle, when cleaning a disc, it should not be wiped in a circular direction; otherwise, the surface will be scratched or warped and the laser beam may not be able to read or pick up accurately the signals on the disc. In this case, the disc will not be maintained in good operating condition and it may "skip" or "stick" or will not play at all. Therefore, it is disadvantageous to wipe the disc in the same direction as its signal representative recesses are directed. Thus, it is recommended to wipe in a circular direction. The larger the intersection angle formed between the wiping direction and the aligned lines of recesses results in optimized cleaning, and the best wiping direction is perpendicular to those lines.
When cleaning the disc, it is better to use both dry and wet components to wipe the disc alternatively, resulting in an optimized cleaning effect.
It is therefore the object of this invention to provide a cleaning device for cleaning the surface of a digital signal recording disc which provides a cleaning element which can wipe the disc in a direction substantially perpendicular to the nearly circular lines of signal representative recesses on the disc surface; that is, the wiping direction and the signal line form a 90 degree intersection angle defining an overall radial direction.
It is another object of the invention to use the cleaning element to do the dry and wet cleaning alternatively for the disc, so that the cleaning element has an optimized effect on cleaning.